Face-Off with a Mountain

Here's your nightly math! Just 5 quick minutes of number fun for kids and parents at home. Read a cool fun fact, followed by math riddles at different levels so everyone can jump in. Your kids will love you for it.

Face-Off with a Mountain

Mount Rushmore is one of the coolest sites in the U.S. It’s a giant sculpture of 4 great presidents: George Washington, Thomas Jefferson, Teddy Roosevelt and Abraham Lincoln. And when we say giant, we mean it: it’s carved into the side of a South Dakota mountain! Their heads are 60 feet tall, and the mountain is hundreds of feet tall, so chipping out those faces was no easy job. Every day from 1927 to 1941, over 400 men and women worked as drillers, carvers, and cooks for the group. Many carvers hung swinging from steel cables to do their work. 90% of the rock was blasted away with dynamite, then they swung back to carve and polish by hand. Since they spent money on the project too fast, the sculpture was never totally finished. But we can still tell which presidents are looking out at us.

Wee ones: What numbers do you say to count the 4 presidents here?

Little kids: President Roosevelt is the one with the mustache. How many presidents are sitting to his right? Bonus: Workers would sell chunks of rock to visitors. If you sold 1 rock for $2, for how much would you have to sell a second rock to make $10 total?

Big kids: The tops of the presidents’ heads are 500 feet above ground. Since their heads are 60 feet tall, how high off the ground are their chins? Bonus: If you sell rocks for either $2 or $7 apiece, how many combinations of the two could you sell to make $23?

Answers:Wee ones: 1, 2, 3, 4.

Little kids: 2 presidents (Washington and Jefferson). Bonus: For $8.

Big kids: 440 feet. Bonus: Only 2 possibilities: one $7 rock and eight $2 rocks, or three $7 rocks and one $2. You can’t sell 0 or 2 big rocks, because then the leftover is an odd number — you can’t fill that by selling $2 rocks.

About the Author

Laura Bilodeau Overdeck is founder and president of Bedtime Math Foundation. Her goal is to make math as playful for kids as it was for her when she was a child. Her mom had Laura baking before she could walk, and her dad had her using power tools at a very unsafe age, measuring lengths, widths and angles in the process. Armed with this early love of numbers, Laura went on to get a BA in astrophysics from Princeton University, and an MBA from the Wharton School of Business; she continues to star-gaze today. Laura’s other interests include her three lively children, chocolate, extreme vehicles, and Lego Mindstorms.